As concerns rise about the health risks posed by per- and polyfluoroalkyl substances (PFAS) in the environment, there is a need to understand how these pollutants accumulate at environmental interfaces. Untangling the details of molecular adsorption, particularly when there are potential interactions with other molecules in environmental systems, can obscure the ability to focus on a particular contaminant with molecular specificity. Often adsorption studies of environmental interfaces require a reductionist approach, where laboratory experiments may not be fully tractable to environmental systems. In this work, we study polyfluorinated dodecylphosphonic acid (F21-DDPA) at the aqueous surfaces of distilled water (the most reduced “environmental” surface) and river water to explore the use of vibrational sum-frequency (VSF) spectroscopy as an experimental probe of fluorinated contaminants at natural environmental surfaces. We demonstrate how VSF spectroscopy offers advantages over nonspecific surface tension measurements when measuring PFAS adsorption isotherms at river water surfaces. VSF spectra of the C–F stretching region selectively probe the presence of F21-DDPA and can be used to extract meaningful structural insights and calculate surface concentrations, even at the complex river water surface. This study highlights the potential for VSF spectroscopy to be developed as a probe of fluorinated contaminants at natural environmental interfaces.
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This content will become publicly available on August 14, 2024
Uptake and release of perfluoroalkyl carboxylic acids (PFCAs) from macro and microplastics
Microplastics and per- and polyfluoroalkyl substances (PFAS) are two of the most notable emerging contaminants reported in the environment. Micron and nanoscale plastics possess a high surface area-to-volume ratio, which could increase their potential to adsorb pollutants such as PFAS. One of the most concerning sub-classes of PFAS are the perfluoroalkyl carboxylic acids (PFCAs). PFCAs are often studied in the same context as other environmental contaminants, but their amphiphilic properties are often overlooked in determining their fate in the environment. This lack of consideration has resulted in a diminished understanding of the environmental mobility of PFCAs, as well as their interactions with environmental media. Here, we investigate the interaction of PFCAs with polyethylene microplastics, and identify the role of environmental weathering in modifying the nature of interactions. Through a series of adsorption–desorption experiments, we delineate the role of the fluoroalkyl tail in the binding of PFCAs to microplastics. As the number of carbon atoms in the fluoroalkyl chain increases, there is a corresponding increase in the adsorption of PFCAs onto microplastics. This relationship can become modified by environmental weathering, where the PFCAs are released from the macro and microplastic surface after exposure to simulated sunlight. This study identifies the fundamental relationship between PFCAs and plastic pollutants, where they can mutually impact their thermodynamic and transport properties.
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- Award ID(s):
- 2032497
- NSF-PAR ID:
- 10443664
- Date Published:
- Journal Name:
- Environmental Science: Processes & Impacts
- ISSN:
- 2050-7887
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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